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Classic Rich Field

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#301 AllanDystrup

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Posted 28 November 2018 - 03:57 AM

.

Jeff, Bill, -- Thank you!
      I have not been able to find much coherent and systematic information and presentation on wide field astronomy with a cosmologic structural and evolutionary perspective, and this is a shame, as I often miss the broader context when observing isolated NGC/IC objects out there in the universe. So yes! there IS a need for a book on this topic, but as I have explained previously, -- I don't currently feel I have the time to write it (see: https://www.cloudyni...ield/?p=7719242). I do hope someone like Glenn with a deeper astrophysical background than I will do it! winky.gif.  When I run out of steam exploring the universe (I'm not a youngster anymore...), I may take a break though and collect, structure and post all my observing reports on a web site / blog.

 

Glenn,

     So, thanks once again Glenn, for your great description of the morphology of coronal superbubbles in the context of the ISM. Excellent explanation of the density gradient from hot coronal bubbles to ISM and to cold dark condensing MC. The eternal cycle of stellar birth and death... As you write Glenn: "The ISM makes for a fascinating subject, made all the more interesting when considered in the context of the full cycle of star formation and death." Dang, I wish you'd sit down and write that book now! grin.gif

 

     Meanwhile , on with :

 

The Orion Complex, Close up:

 

 

     It’s closing in on midnight this evening in late November (2019-11-25, 23:30 Loc CEST, UT+1), as I’m out in my suburban backyard for a study of the Orion-Eridanus super-bubble plus some closer-up views of the Orion A and B molecular clouds in the young Ori OB-1d associations E of Alnitak in the Belt and behind the Sword. There are a couple of obstacles though: first there’s a 27dy/90% moon blazing close by in lower Gemini at 40° and less than 15° E of central Orion. And second: the transparency is rather poor (4/7) due to a combination of high humidity (93%) and low temperature (-1°C, with the DewPt at -2°C), which has resulted in a high frosty haze creating a halo around the moon and white contrails, when planes cross through the field of view. This is rather magical and beautiful in fact, and as is often the case with this kind of Autumn weather here in Denmark, the seeing is quite good (8/10), but all-in-all the “celestial light pollution” is reducing the SQM to 18.3 (NELM 5.2) and that is not conductive to my planned study of the faint Ori-Eri super-bubble, or even the “Angel Fish” around the Lambda-Ori OB group.

 

     I therefore decide to concentrate tonight’s observations on the relatively bright MC-complexes in the ORI OB-1d association. I start with a 6.5x in 5.5° FOV overview of the region, spanning the sky from Orion’s Belt down to and including the Sword. I’m using my 60mm f/6 finder scope + a TV 55mm EP with a 6nm Hα filter in front and my 4G NV behind the EP. WOW… What a splendid cosmic panorama (cosmorama?)  stretching from the Flame, Dagger and Horsehead at Alnitak (ζ Ori) towards the NE, to the bright M42/M43 nebulae towards the S, surrounded by NGC1981 and the Running Man above, and NGC1980 (the Iota Ori complex) below. A beautiful wide field view of stars, ionized nebulae and DMC, which is where NV really excels!

 

Ori OB-1d AB MC.jpg
*click*

 

Ori OB-1d AB MC B.jpg
*click*

 

 

      I now increase the magnification to 28x in 1.5° FOV, using a 13mm EP and a 12nm filter to have a closer look at the young Orion OB-1d molecular clouds; First the Ori A-MC with the M42/M43 nebulae. The view is rather good for NV with a 60mm scope (I think), -- The core of M42 (the Huygens Region with the Trap) is easily burned out of course, but by varying the gain on the NV device and the ISO on the phone app I can study quite a lot of details in the wings and body close to real-time, though not at the same level of detail as using longer exposure live video with stacking (HH objects, proplyds/YSO, outflows, bow-shocks etc.).

 

Ori OB-1d A MC.jpg
*click*

 

Ori OB-1d A MC B.jpg
*click*

    

    

         I close with a study of the Ori B-MC  (L1630) east of Alnitak. Now this is quite an interesting view compared to what I’ve been able to see with glass only, -- the Flame (NGC2024), Dagger (IC434) and Horsehead (B33) are all easily seen in a FOV that includes the multiple OB-system σ Ori with the central Σ762- Σ761 components plus several more outlying type-B members (of which I’ve labelled 4 below). The central σ Ori AB-components are hot massive stars of type O9.5V + B0.5V, and they are responsible for ionizing the emission nebula known as "Orion’s Dagger” (IC 434).  To the E of IC434 is the B1.5-IV subgiant star HD37903 which is illuminating the bright reflection nebula NGC2023, but this RN of course does not show up in 12nm Hα (I’ve marked the star on the snapshot below anyway). The dense MC of NGC2023 contains a small cluster of Young Stellar Objects (YSO), including proto-stellar HH objects and Pre Main Sequence (PMS) T-Tauri stars. Silhouetted against the bright HII region IC434 (Orion’s Dagger) is the dark cloud of dense gas and dust B33, with an emerging “pillar” known as the Horsehead Nebula. The source of the ionization of IC434 as well as the photo-evaporation of the Horsehead pillar is as mentioned the σ Orionis multiple star system. Finally, E of Alnitak is seen the extensive HII region NGC2024, the Flame Nebula, with a broad N-S dark lane and a heavily obscured embedded cluster with associated HII regions blowing out from the N but still bounded by a sharp ionization front towards the S, and two filamentary bubbles: one E and one W. The Flame cluster contains many YSO (HH objects, accretion discs)  and also of course some hot ionizing stars, though the ionization sources of the nebula are too obscured to be identified.

    

    

     It’s getting late (early rather), so I take some quick photos with my iPhone. The phone is running low on power though (the lithium battery does not like temperatures below zero), so I have to hurry with the Flame/Horsehead snapshot before the phone closes down. I don’t get the gain and ISO settings exactly at its best for this object, so the image is somewhat grainier than was the view, -- but you should be able to see what I’m talking about…

 

Ori OB-1d B MC.jpg
*click*

 

Ori OB-1d B MC B.jpg
*click*

 

   -- Allan

 

 

__________________________________

PS:

Some final notes on my latest Orion studies:

 

It has been interesting to see all the Orion OB-associations that I have studied previously coming together in these wide field NV observations,
• from the young (<5 Myr) λ-Orionis group in the N around Meissa (Cr69, in the Angel Fish),
• over the oldest OB1a group (~10 Myr) S of Bellatrix (γ Ori),
• to OB1b (~4½ Myr) around the Belt and OB1c (~4 Myr) forming the Sword with the star clusters NGC 1977/80/81 from σ to ι Orionis.
• Especially conspicuous are of course the very young OB1d (< 2 Myr) subgroups including:
     - The Ori-B MC: the stars (NGC2024) in the Flame and Dagger Nebulae E of at Alnitak in the Belt, plus
     - The Ori-A MC: the stars in the M42/M43 Nebulae behind the Sword (part of a larger S-shaped OMC filament (Orion Molecular Cloud)


For more context on the Orion OB-associations, see my previous posts higher up in this Rich Field thread:
• Lindblad’s Ring and Gould’s Belt: https://www.cloudyni...ield/?p=7693829 ff.
• Orion Blue Stream: https://www.cloudyni...ield/?p=7740223
• Orion OB-1 association: https://www.cloudyni...ield/?p=7682143

 

The ages and locations of the various Orion OB-1 subgroups indicate that star formation has propagated through a “sweep-up, compress and trigger” process through the proto-Orion cloud in a sequential manner:

• from 1a S of Bellatrix -> to the 25-Ori and 1b subgroups,
• from 1b (the Belt) subgroup -> to the λ Orionis and 1c subgroups
• through the 1c subgroup (Sword) from the N
     via the NGC 1981 and 1955 (“Running Man”) groups 
     down to the ι Ori group (NGC 1980) in the S.
• finally (in the past few Myr) through the 1d subgroups with:  
      - the Orion A molecular cloud (M42/M43) behind 1c (the Sword), and
      - the Orion B molecular cloud (Flame/Horsehead) E of the Belt at Alnitak. 

 

The cluster around ι Orionis (NGC 1980) in Orion OB-1c is probably the parent of the two run-away stars AU Aur and μ Col that were kicked out of the cluster by the supernova explosion which created Bernard’s Loop, the E wall of the great Orion-Eridanus Super-bubble. For detail studies of the different sections of Orion OB-1, see these posts:
• Lambda Ori (Angelfish): https://www.cloudyni...ield/?p=7689747
• 1a subgroup : https://www.cloudyni...ield/?p=7682150
• 1b subgroup (Belt) : https://www.cloudyni...ield/?p=7683950
• 1c subgroups (Sword) : https://www.cloudyni...ield/?p=7685870
• Sigma Orionis group: https://www.cloudyni...ield/?p=7684634
• 1d subgroup (M42/43): https://www.cloudyni...ield/?p=7685902
• Ori OB-1 Runaway stars: https://www.cloudyni...ield/?p=7687660

 

      /A


Edited by AllanDystrup, 28 November 2018 - 07:57 AM.

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#302 GlennLeDrew

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Posted 28 November 2018 - 03:40 PM

Allan,

I read a paper back about 2000-ish in which it was posited that iota Ori *might* be also an ejected member, along with AE Aur and mu Col, from the Trapezium. If all three stars were kicked out in the same ejection event, it could (?) suggest a former hierarchical triple in which the more massive star received a smaller 'kick' than the other two lightweights.

 

I wonder if this theory has been revisited, using GAIA data?

 

Perhaps the notion has already been rejected/refined...


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#303 Mr. Bill

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Posted 28 November 2018 - 04:58 PM

Allan and Glenn, how about a collaboration?

 

I'll buy copy #1....signed of course.

 

cool.gif


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#304 AllanDystrup

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Posted 29 November 2018 - 08:20 AM

Bill, -- I'll sign you up! That one book will be expensive tho' lol.gif 

 

Glenn,

<Correction: DANG! you said iota Ori, and for some reason I read sigma Ori. So the info below does not apply directly…

   Or put another way: yes! certainly iota Ori was part of the stellar shuffling resulting in the two runaways.  wink.gif >

 

Interesting thought, -- but I doubt that it can be substantiated.

A traceback of the proper motion of σ Ori (->NE of the Horsehead) does not fit too well with the ONC (Orion Nebula Cluster) as a source, and the speed of proper motion should be ~100km/s which i think is much higher that the speed of σ Ori (? I haven't a datapoint on that). So my money is on σ Ori being native to the northern Orion OB-1c formation. 

 

Here's some more info on the subject:

 

 

Sigma-Ori.jpg
*click*

 

   -- Allan


Edited by AllanDystrup, 29 November 2018 - 08:35 AM.


#305 CelestronDaddy

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Posted 29 November 2018 - 08:47 AM

You guys amaze me with such in depth knowledge 👍🏻

#306 GlennLeDrew

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Posted 30 November 2018 - 01:58 AM

Another perspective-expanding tidbit regarding the ISM...

 

Imagine contracting Galactic Pipeworks to extrude a pipe some 10,000 light-years long and of inside area of 1 square metre (inner diameter of 707mm.) As part of the contract they fabricate a gas-tight piston to fit. This tube is placed in interstellar space, within the Galaxy's mid-plane. The near end of the pipe is capped, and the piston inserted into the far end. Then the piston is rammed down, stopping just 1m short of the bottom.

 

After plunging some 10,000 l-y, that last 1metre of interstellar gas will have a volume of 1 cubic metre and be compressed to equal the density of earthly sea-level air. The mass of this gas will be roughly 1 kg.

 

Contained within that gas sample will be about 10 grams of smoke particle-sized dust. This is because the ISM has become increasingly polluted over the history of the Galaxy, principally by the effluvia of dying red giants stars. About 1 per cent of the ISM mass is this 'star soot', which is ~10g/kg.

 

Imagine a plexiglass cubic box of dimensions 1m on a side (volume 1m^3) containing 10g of cigarette smoke (not unlike interstellar dust in terms of particle size). The visibility within would be measured in centimeters.

 

The ISM in our Galaxy is *extremely* polluted. Excluding some very small-scale variations, in the main this stuff is more or less uniformly mixed through all phases of the ISM (except perhaps the hot coronal bubbles of million-degree gas blown out by massive stars and supernovae.) The degree of transparency of the ISM is thus a pretty direct indicator of the gas density. Which is why the denser molecular clouds limit visibility within to a fraction of a l-y, while the warm ISM permits to see for several or tens of thousands of l-y. In all instances the gas involved contains roughly the same mass fraction of dust.


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#307 AllanDystrup

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Posted 09 December 2018 - 04:15 AM

.

 

      Back on the grid again…  The latest Windows Update crashed my PC and corrupted my windows installation beyond repair. Total FUBAR! No loss of data on the hard disk though, but it’s back to square one with all the programs I had on my pc – buy/download, install, authorization keys, configuration, optimization… “Hours of fun for the whole family”.  wink.gif --  Well, I can boot a new Windows now at least, so here’s the report from my latest journey into the Universe (fantastic that our Cosmos only booted once, and it’s still running without any updates at all. Go figure, Mr. Gates…)

 


Sh2-264, The Angelfish.

     
    It’s a wonderful early morning in the start of December (2018-12-05, 01:30 Local CEST, UT+1). A high pressure has settled over Germany, guiding relatively temperate and dry air up over Denmark (Temp.: 2dg C, Hum.: 59pct, Dew-pt.: -5dg C), so the transparency is fine (5/7), and though the seeing is only medium (6/10) due to a southerly wind blowing from the high pressure, this is the best night for stargazing I’ve had for the past couple of months. The 5% / 26dy Moon is well out of the way low in the W, so the LP is also good for my suburban backyard tonight (SQM 18.1, NELM 5.1). All set for having a look at the HII clouds in the Orion-Monoceros part of our Milky Way!

     

     For my first target tonight, I choose Sh2-264, the “Angelfish” nebula surrounding the Lambda Orionis cluster (Cr69) that forms the Head of Orion. Lam Ori (Meissa) is a blue giant at ca 1.1 Kly distance from our solar system (note that the orange subgiant G9-IV Phi2 Ori SSE of Meissa is a foreground object at only ca 116 Ly distance, and thus not part of Cr69 in the Angelfish).

     
     Meissa is an O8-III normal giant, -- the only type-O star in the Lam Ori OB association, but accompanied by a dozen B-stars. Meissa is the exciting star of the ionized HII nebula Sh2-264, that is expanding into, sweeping up and compressing the surrounding shell of neutral Hydrogen, the darkest portions of which are denoted B35 (towards the SE) and B30 (towards the NW). Meissa is at the centre of the Lam Ori OB group of massive hot stars, with most of the lower-intermediate mass emitting objects (Ae-Be & T-Tauri stars) located in a SE-NW oriented “Bar” from B35 to B30 inside the Angelfish nebula;  This distribution reflects the original highest density of the ancient Lam Ori molecular cloud, which has now mostly been swept out by the expanding HII region into the surrounding shell,  leaving the many young stars visible.

     

     

Angelfish-W.jpg

*click*

Angelfish-B.jpg

*click*

          

          

     I've previously observed the Lam Ori cluster with glass only  (Vixen FL-55S/440, Mas 2" 32mm for 14x @ 6dg FOV, see:  https://www.cloudynights.com/topic/565226-classic-rich-field/?p=7689753), so next up tonight I'd like to repeat this with a comparable setup (TS 60/360, TV 2" 50mm for 7x @ 6½ FOV) , but this time adding a 6nm filter + NV. The view of the stars is of course blowing away what I was able to see with glass eyes only, and there is also some nebulosity seen in and around the Lambda Orionis OB association in this close up observation, but the Angelfish is better framed swimming in the 1x 40dg wide field pond as shown above.

     

     LamOri-W.jpg

*click*
LamOri-B.jpg
*click*

     

To-be-continued, 

   -- Allan


Edited by AllanDystrup, 09 December 2018 - 09:37 AM.

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#308 AllanDystrup

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Posted 11 December 2018 - 04:46 AM

.

 Monoceros HII Regions.

     

     

      We’re well into this early December morning (2018-12-05, 02:00 CEST UT+1), after I’ve finished my observation of the λ-Orionis OB-association in the Angelfish Nebula. Orion has now crossed the meridian, so next up I point my telescope towards the region E of Bernard’s Loop to start with a wide field view of the ionized gas clouds in the Monoceros-Orion region. This is one of my favorite areas in the night sky, rich with OB-associations, supernova remnants and gas/dust nebulae of all sorts (emission, reflection, dark). I’ve previously described the region’s OB-associations starting here: https://www.cloudyni...ield/?p=8190017 ff., followed by more detailed overviews and obs-reports here:

     

     

     Tonight, I’ll concentrate on the bright emission nebulae surrounding the MON OB-1 and OB-2 associations using my NV gear, as these nebulae are hard to observe with glass eyepieces and live video (without stacking), and as the reflection nebulae (R1 and R2 regions) are pretty much out of reach for NV. I start with an overview of western MON using NV at 1x (unity) magnification with a 12nm Hα filter in the nose;  I get a great 40° view of the field, including all of the Orion OB associations and surrounding ionized clouds towards the W (Angel Fish, Bernard’s, Flame-Dagger, Sword), plus the major Monoceros OB associations with their ionized clouds below the feet of Pollux towards the E (Fox Fur, Rosette). The Sh2-273 Fox Fur nebula is faint but visible around 15-Mon (= S-Mon) in the Xmas Tree cluster, while the Sh2-275 “Rosette” nebula is an obvious bright patch with the foreground star 12-Mon close to the center.  What a wonderful sight!

 

Mon-1x-12nm-W.jpg
*click*

Mon-1x-12nm-B.jpg
*click*

 

     

 Fox Fur

     

     Starting from the N I first zoom in on Sh2-273, the extensive molecular cloud complex spanning >2° on the night sky S of the feet of Pollux.  At the E edge of this HII cloud is seen a large arc of nebulosity that is probably a large windblown shell or supernova remnant (SNR); at the W edge of this shell structure is located Mon R2 with the reflection nebulae NGC 2245 & 2247, which I have previously observed using glass (see link above), but that is out of reach with a narrowband Hα-filter.

     

     Cradled by the E nebula arc is the Mon OB1 association (NGC2274, Xmas Tree cluster) at a distance of 0.76 Kpc in our own local spiral arm. This is a very young association (only ~3 Myr) with the massive multiple O7-V star S Mon (15 Mon) as its primary member featuring a close O9.5-V secondary companion. The Mon OB1 contains >17 mid to late type-B stars concentrated in two cloud core “clumps”:  one around and just SW of S Mon, and another just N of the tip of the Cone DN. These two sub-clusters also both have many intermediate and low mass (< 3 Msolar) new-born stars, which have been studied intensively due to their relative proximity and lack of significant foreground extinction. S-Mon is the primary ionizing source of Sh2-273, including objects like the “Fox Fur” nebula immediately NW of S-Mon, and the bright rimmed “Cone” nebula to the S. I studied Mon-OB1 using my small 60/360mm refractor with a 55mm eyepiece plus my NV monocular. Here are a couple of snapshots through this setup, using my iPhone-5 with the NightCap App: the X-Mas Tree cluster is beautiful in the unfiltered view, and the Fox Fur EN is evident in the 6nm Narowband Hα view, where also several dark nebulae (B37-38-39) can be seen, and even the dark "Cone Nebula" can be glimpsed (click on image...).

 

 

6½x-50mm-NoF-6nm-FoxFur B.jpg
*click*

 

6½x-50mm-NoF-6nm-FoxFur W.jpg
*click*

 

Next up: The Rosette...
  -- Allan


Edited by AllanDystrup, 11 December 2018 - 03:00 PM.

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#309 AllanDystrup

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Posted 12 December 2018 - 09:31 AM

.

  Monoceros HII Regions, continued

 

Rosette

     

    

           From Sh2-273 (the “Fox Fur”) I now pan S to the extended Sh2-275 emission nebula (the “Rosette”): a large bright HII-region with a central cavity evacuated by stellar winds from the Mon OB2 association. On the way I first pass a fainter arc of nebulosity close to the NE of the Rosette: this is a small S part of the large Monoceros Loop, a ~100.000 Yr. young supernova shell (SNR).

     

     All in all, Mon OB2 contains >70 high mass stars, 7 of type O and 24 of type B.  The family of MON OB2 clusters were created in a sequential subgroup formation, starting with Cr 107 (age 15 Myr), followed by Cr 106 (5 Myr) and then finally and recently (a few hundred Kyr ago): the central NGC2244 OC, right out of the delivery room, and still shrouded in its bed sheets of gas and dust (the Rosette). NGC2244 in Mon OB2 is roughly the same age as the central cluster NGC2264 in Mon OB1 in our Local arm, but Mon OB2 is much more distant at ~1.7 Kpc (5 Kly) in the outer Perseus spiral arm.

    

     MON-OB2-B.jpg

*click*

     

     

     The Rosette emission nebula (NGC 2246, NGC 2237-38) is primarily ionized by strong UV radiation from two ultra-hot (~50 KK) rare type O3.5 V stars: the 6.7m star HD16150 at the center of the rectangle of stars, plus the 7.2m star HD46223 just SW of the foreground star 12 Mon (more on these hot early type-O stars plus the interesting huge, blue O8 supergiant double HD47129 aka. Plaskett’s Star in this link: https://www.cloudyni...ield/?p=8234597).  The Rosette shows a somewhat brighter patch to the SE (NGC2246) and another to the NW (NGC2237-38), while the central cluster of the OB2 association has been catalogued as NGC2244, with the brightest star 12 Mon also designated NGC2239 (a little confusing, yes?). In the NW quadrant of the Rosette some dark veins can be spotted (best seen on my small insert phonetography in the annotated picture below). These are caused by obscuring dust bands containing many Bok Globules. On the night sky the Rosette Nebula is about as large as the great Orion Nebula (M42), but as it is 3x as far away, it is intrinsically also 3x larger (115 Ly diameter) than our neighbour M42 (40 Ly diameter).

     

MON-OB2-W.jpg
*click*

     

     

  -- Allan


Edited by AllanDystrup, 12 December 2018 - 11:14 AM.

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#310 Tyson M

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Posted 12 December 2018 - 11:28 PM

Allan, the Lam Ori cluster NV image looks amazing and full of stars! Angelfish, Rosette, ect all look stunning. 

 

Indeed these areas are full of beautiful targets with glass eyepieces, and extend themselves further and multiply in number with NV.


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#311 Eddgie

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Posted 13 December 2018 - 09:19 AM

As always, some great observations.

 

The 1x view of Cone Nebula across to Barnard's Loop and Anglefish is one of the most amazing views in astronomy.  


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#312 AllanDystrup

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Posted 04 January 2019 - 02:19 AM

.

The Orion-Eridanus super-bubble

     

     

     After several weeks of cloudy nights, the weather pattern finally changed from a SE continental balmy and humid airflow to a high pressure settling over the UK and pushing cool and dry polar air up past the Norwegian mountainsides and then down over Denmark. The change in weather started with a storm from the NW, but then tapered off to a calm and clear starry night with both transparency and seeing well above average.

     

     So of course, I’m out now on this early January evening (2019-01-02, 21:00 CEST, UT+1) to continue my studies of the HII clouds in the winter part of the Milky Way. Before proceeding to the emission nebulae S of the Rosette in Monoceros, I decide to see if I can first poke my head into the Eridanus Loop part of the Orion-Eridanus super-bubble. 

      
     The Orion-Eridanus super-bubble was first described as late as in the 1970s in a radio survey of the sky at 21 cm wavelength. The bubble is located at 1.5 Kly from the sun, below the disk of the Milky Way west of the Orion constellation on the night sky, and it is the result of three previous generations of stars having spawned at least 6-7 supernova explosions in the past 10 million years. The explosions have swept out a cavity to a diameter of ~1 Kly containing rarefied gas heated to millions of degrees. The cavity is surrounded by a cool outer wall of overlapping nested supernova shells, parts of which can be seen as large ionized H-II arcs: the Barnard's Loop (Sh2-276) to the E and the Eridanus Loop (Sh2-245) to the W.  The super-bubble is currently expanding with a speed of about 20 Km/s... Talk about a wide field object shocked.gif .

     

Orion-Eridanus SB.jpg
*click*

       

     

     The Eridanus part of the SB is farther from the sun and also at a greater distance from the Orion star forming region, and hence it is considerably fainter and more difficult to study than the Bernard’s Loop part. I first try to spot it at 1x (unity) with my NVD+6nm filter; There is a trace of delicate, faint luminosity running from λ Tau down south, passing west of Nu Tau, and further south towards 32 Eri. This corresponds to the brightest “Arc A” of the Eridanus Loop filaments, and so I could just glimpse that (confirmed upping the magnification to 6½x using my 60mm f/6 with 55mm EP + 6nm Hα); The other parts of the Eridanus Loop filaments were not seen, neither at 1x nor with certainty at higher magnification.

     

Eridanus Loop - Arc A.jpg

*click*

 

     

     Next up: the EM nebulae S of the Rosette in the winter Milky Way,

          -- Allan


Edited by AllanDystrup, 04 January 2019 - 08:57 AM.

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#313 AllanDystrup

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Posted 05 January 2019 - 03:51 AM

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Southern Monoceros: Sh2 280-282 and 284

     

     

     The southern area of Monoceros, bordering on Canis Major (CMa), is characterized by a number of scattered gas & dust clouds with clear views in between featuring an abundance of open clusters, right out towards the rim of our Milky Way.

 

 

MON-OB2 CMA OB1 #1.jpg
*click*

MON-OB2 CMA OB1 #2.jpg
*click*

     

          

     In a line on the night sky from the “Rosette” (Sh2-275) SSE down the Milky Way stream to the “Seagull” (Sh2-292-296) there’s a group of fainter HII-clouds with designations from Sh2-280 to Sh2-291; The largest of these are described here, with their estimated distance (and ionizing OB stars): 

 

  • Sh2-280 and Sh2-282: both part of Mon OB2 in our Local Arm at 1.5 Kpc near the edge of the Rosette cloud (Sh2-280: HD46573 O7-V and Sh2-282:HD47432 O9.5-III)
     
  • Sh2-284: part of the Monoceros Arc in the outer Norma spiral arm, at a whopping 7.9 Kpc (Do95 OC with HD 48691 B0.5-IV)

 

S Rosette W.jpg
*click*

S Rosette B.jpg
*click*

 

 

     Next up we move further down S in the Winter Milky Way, to CMa-OB1 where the Seagull nests...

 

     --- Allan.


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#314 AllanDystrup

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Posted 06 January 2019 - 02:01 AM

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Canis Major OB1, the Seagull Nebula.

     

     
  Tracing the Milky Way further down south, we now come across a very rich part of our local galaxy arm: right on the border between Monoceros and Canis Major, at a distance of ~1 Kpc, we find the CMa OB1/R1 association with several open clusters, one large plus a handful of smaller ionized hydrogen clouds lit up by more than 17 hot young massive stars (4 of type O), and a generous handful of reflection and dark nebulae thrown in for good measure. Here at 56⁰ N latitude in early January at 22h local time, CMa OB1 is still low  ~15⁰ Alt. in the SE  (culminating at 23⁰ Alt. ~1h past midnight). I find it easiest to locate CMa-OB1 by star hopping from Sirius (just above my neighbors rooftop), first up to the nose (Theta) of the big dogie, and then panning east 2½⁰ in RA till I hit upon the star rich area. The area is spectacular, strewn with many ~6m young hot stars and knots of open clusters, -- even as seen at 6½ x magnification using a TV 55mm Plössl eyepiece in my 60mm f/6 finder.

     
   Prominent among the OCs in the CMa OB1 area are NGC 2353 (76 Myr, 1.2 Kpc) plus the younger NGC 2343 and 2335 (both ~20 Myr and 1.2 Kpc), but most spectacular (at least in narrow band Hα) are the gas clouds at ~1 Kpc distance from which are born the dozens of young and massive type O and early B stars in the CMa OB1/R1 association. Around ½ Myr ago one of the early stars in this association went supernova, leaving a 3⁰ large expanding shell in the surrounding neutral hydrogen, plus a a shock front (SNR)  that has pushed out into a ring of emission  nebulosity including the HII regions Sh2-292-296-297 to the W plus a number of fainter nebulae to the N and E. The O6.5-V runaway star HD54662 may well have been kicked out of the early CMa OB1 by this SN explosion, that also triggered star formation in the swept up clouds, which today are lit up by a patchwork of emission and reflection nebulosity (the CMa OB1/R1), interwoven with dark nebulae (such as L1657-1658).

     

     

     Due to the rather low altitude (15⁰) of the area, the transparency of the view tonight is somewhat reduced, and thus the observations (and the snapshots) are not as contrast rich as they can be; The EM in the head and wings plus the S wing tip of the Seagull are obvious, but the smaller HII clouds (Sh2 295, 293, 298) are only glimpsed.

 

MON-OB1-R1 W.jpg

*click*
MON-OB1-R1 B.jpg
*click*

 

 

I make a decision however to revisit the CMa-OB1 area closer to culmination, and using a larger magnification of ~16x. Sh2-298 (“Thor’s Helmet”) btw. is not part of CMa OB1 but rather a combination of an emission arc plus a wind-blown bubble at a large distance of ~5 Kpc.

 

     -- Allan


Edited by AllanDystrup, 06 January 2019 - 03:46 AM.

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#315 AllanDystrup

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Posted 06 January 2019 - 03:34 AM

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CMa OB1, continued...

     

     

Follow up on CMa OB1, 2019-01-05, 23:00 Local DST (UT+1).

     
     It’s new moon tonight, but with an increasing cover of low clouds moving in at the horizon from the SW. The clouds partly obscure the MON/CMa border where CMa-OB1 is located, but I am able to get some peeks at the area in the holes between. What is worse is the high humidity (95%) plus the temperature dropping fast from 1⁰C down towards the Dew-Pt at 0⁰C; This will be accompanied by a quick buildup of fog that will reduce the transparency from 4->1/7 in the next ½h, so I have to move fast.

     
     The weather is calm, the seeing is good at 8/10 and the LP is fine for winter time in my suburban backyard at SQM 18.9 (NELM 5.5). You can see the location of my “red” refractor on the LP map below, at the N outskirts of Copenhagen, 56N in Denmark:

 

LP-Alleroed.jpg

     
          

     I start with star hopping from Sirius, N to Theta CMa, then E to CMa OB1. I get a good view of the Seagull EM (Sh2-296/92/97), and take care this time to also properly include Thor’s Helmet (NGC 2359, IC 468, Gum 4), where I can just glimpse the central windblown bubble, created by the Wolf-Rayet star WR7, and with two “horns” of emission nebulosity bending in an arc W of the bubble; Not bad I’d say, for 6½x mag in a 60mm finder... wink.gif 

 

SH-TH.jpg

[12nm Ha FILTER]
*click*

     

     Just as I’m preparing to bump up the mag on the Helmet... – alas the temperature drop hits the DewPt at 0⁰ and fog start to quickly condense out of thin air. Beautiful to observe in a way, together with the white wind vanes of water vapor trailing horizontally from the neighboring chimneys in this cool calm winter weather..., -- but all this leaves me after 10 min with only Sirius burning through the veil.

     

So, I still need that closer look at the Helmet... imawake.gif

 

     -- Allan


Edited by AllanDystrup, 06 January 2019 - 01:31 PM.

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#316 PEterW

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Posted 06 January 2019 - 04:17 PM

Impressive, pulling in the eridanus loop from less than perfect skies. Must have been good transparency! Did the gain control help make the object more visible by reducing the scintillation noise? I have only just managed to glimpse it once after many tries!
I am surprised the seagull was faint, certainly looks quite bright when I have seen it. Looks like you are having fun with NV.

PEterW

#317 AllanDystrup

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Posted 07 January 2019 - 01:49 AM

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PEterW,

 

     Yes indeed, on the night I observed the Eridanus Loop both transparency (5/7) and seeing (7-8/10) were well above average after a NW storm had swept across the country, and the LP on this night was also better than usual for my location (SQM 19.5 ~NELM 5.7).

 

     Note though that I only saw (as in "glimpsed") the N part of the brightest A-Arc of the E. Loop, -- the rest I was not able to see; And this object has probably been the most difficult for me to nail of all the HII-clouds I have aimed at since I got my NVD.

 

     On this observation I had the gain control on the NVD high up (but not maxed out) to be able to trace the E outline of the A-Arc, and the Arc was easiest to identify using NightCap with averaging to smooth out noise. (Not sure I could have identified it with certainty without NightCap.)

 

     

   As for the Seagull, I wouldn't say it was faint in my observation, though certainly not as blazing as the Gamma CYG, NA-Pelican, Flaming Star, Heart&Soul, Rosette etc. This is probably due to  the lower altitude of the object when I observed it (15dg), but also that I preferred the broader 12nm Ha-filter and a lower gain setting for balancing out filter de-tuning and central light saturation (hmmm, donno the technical term for this) of the view.

 

     I'm still playing around with the parameters for best views viz. magnification, intensification (gain), contrast, filter de-tuning plus on NightCap: exposure, ISO-setting, averaging... Also of course depending on the object of choice. But hey! A lot of fun, and most important: Alohomora!! opening the locked door to the wonderful world of the huge realm of Milky Way hydrogen clouds, partly lit up by scattered young OB-associations of massive hot giants. What - a - treat!! shocked.gif

 

     -- Allan


Edited by AllanDystrup, 07 January 2019 - 02:05 AM.

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#318 AllanDystrup

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Posted 05 February 2019 - 02:33 AM

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The Seagull and The Helmet – close up

 

 

     It’s an evening in early February (2019-02-03, 21:00 local CEST, UT+1). The new moon is far below the horizon towards the NW, so the LP is “well controlled” for my suburban backyard condition (~NELM 5.7). Both seeing and transparency are around medium, -- calm here at the Earth’s surface with a temp. below freezing at -1⁰C and a moderate humidity (76%), but as the dew point is close by at -4⁰C, there’s a light haze building up on the horizon and starting to drown out all stars below 20⁰ altitude. Low towards the S, I can only spot δ and ε in the hind leg of Canis Major, and higher up there’s a turbulence in the atmosphere resulting in some star twinkling, -- but HEY! considering it has been a month since there were clear skies here north of Copenhagen, this will have to do, when starry nights are few...

    
     The season is progressing and the outer rim of the winter Milky Way has already rotated far W, but before Orion goes to bed and the window above the Milky Way opens to the spring fountain of galaxies, it’s time to say goodbye to the nebulae and OB-associations of our own galaxy. My project for tonight is to have a closer look at the Seagull and Thor’s Helmet nebulae on the border between Monoceros and Canis Major.

    

    

     My star hop is as usual for these objects: from Sirius, first to the nose (θ) of the Big Dog, then due E in R.A. till I hit the star-rich region of CMa OB1. My refractor is the small TS 60/630mm @ f/4.7, with a 6nm Hα filter, and I start with an overview at 8.8x in a 5⁰ field of view.

 

     The Seagull is seen with a little more detail than I have observed it previously: the dark “mouth-area” (LDN 1657) stands out clearly, as do the “knots” of nebulosity around the B2 giant HD52721 (Sh2-293) and at the tip of the S wing (Sh2-297). There’s a fine contrast between the 1 Myr old large shell of bright Hα-emission so clearly seen in the wings of the Seagull (Sh2-296 / Gum-2 / IC-2177), and the dark molecular clouds pushed out towards the W by the expanding supernova ionized front. The SNR has initiated the star-forming in the region, leaving an abundance of early hot and massive stars (CMa OB1,) that includes several type O and early B stars setting these nebulae "on fire, off the feet of Orion"...

 

Seagull-00.jpg
*click*

 

     Switching now to a higher magnification of 22x in 1⁰40’ field of view (13mm ETH), I start panning N->S down the Seagull profile (Sh2-296): the view is breathtaking at this higher magnification, especially in the field that includes the “head” (Sh2-292) of the Seagull; This part is lined with dark nebulae (LDN 1657, “the CMa Dark Complex”) which makes for a contrast rich dramatic view, that is best studied in dynamic visual observation, and seems somewhat “flat” when viewed in a phone snapshot. Anyway, here’s the sequence of snaps I made during the “flight over”:

 

Seagull-01.jpg
Seagull-02.jpg

Seagull-03.jpg
*click each*

 

 

Next up: Thor's Helmet

     -- Allan

 

 


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#319 AllanDystrup

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Posted 05 February 2019 - 03:29 AM

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[The Seagull and] the Helmet – close up

 

    

     The temperature is dropping, and there’s a thin layer of ice forming on the dew-shield of my refractor, so I decide to close the evening with a close up view of Thor’s Helmet. At 8.8x in a 5⁰ field, the Helmet is seen as just a small bi-partite C-shaped smudge, which -- with intensified imagination -- can be conceived as the N bubble plus the S filament of the object. I do need more magnification here though...

    
     Upping the mag. to of 22x in 1⁰40’ field of view, the true character of the object starts to emerge. I can now clearly see the extremely hot central star HD56925 (aka WR7, a WN4-class Wolf-Rayet star), surrounded by a wind blown bubble of dust and gas (NGC2359) released by the pre-supernova spasms;

 

     Also clearly seen now are the two nebula parts (Sh2-298) stretching out NW and SW, forming a filamentary shell which consists mostly of swept-up interstellar gas, and thus are not material shed by the WR-star. These nebula filaments of course form the “horns” of the bubble “Viking helmet” (or the “ears” of the Cyclops Rabbit head, as you prefer to see it...) --  Marvelous! laugh.gif 

 

 

ThorsHelmet-00.jpg
*click*

     -- Allan


Edited by AllanDystrup, 05 February 2019 - 03:40 AM.


#320 AllanDystrup

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Posted 13 February 2019 - 07:29 AM

.

So you should view this fleeting world --
A star at dawn, a bubble in a stream,
A flash of lightening in a summer cloud,
A flickering lamp, a phantom, and a dream.


[from the end of the Diamond Sutra]

    

    

     

     And yes, when studying the wide field structures of our neighborhood in the universe, what I see are bubbles, small and large, floating in the stream of the Milky way, young stellar associations still veiled in Hydrogen sheets, stellar nurseries cradled in the arms of our galaxy. Flashes of flickering lamps and phantoms, -- a dream indeed, but a beautiful one to behold, while it lasts...


     To sum up my most recent observations, I’ve studied the structures of the Orion-Eridanus superbubble (with the λ-Orionis ring, Bernard’s Loop and the Fishhook), and to the N of this bubble (in galactic coordinates): The Flaming Star and Tadpole in Auriga plus the Fox Fur and Rosette in Monoceros. Floating further down the stream of the winter Milky Way, cradled in the Perseus arm, are the GUM 2 SNR bubble with the Seagull plus the Gum 8 bubble in CMa and the Gum 12 Superbubble in Puppis-Vela, which I have not studied yet.

 

CMa Ha Overview.jpg
*click*

 

 
     Tonight (2019-02-11, 21:00 CEST~UT+1) I plan to sail from Gum 2 (the Seagull) further S on the night sky with my big 4” refractor to see if I can catch a glimpse of the GS234-02 and Gum 8 bubbles in southern CMa. The temp is just above freezing at 1⁰C, the humidity is comfortably low (for my conditions) at 70% and the DewPt is down at -4⁰. There’s a 40% (7dy) moon at 26⁰Alt in the tail of the whale (Cetus) in the SW, but it’s heading towards a neighboring tree, so it will pose no problem for my observations. Transparency (5/7) and seeing (6/10) are both just above medium and the LP is relatively good at NELM ~5.6 (SQM 19). All set to throw the mooring and head down S in the Milky Way stream.


    I start from the Gum 2 SNR bubble with the Seagull. It is interesting to compare the previous views of the Seagull through my 2” finder with the view through my 4” refractor; -- The 2” is doing rather well in comparison actually, but I had to push up the ISO to max level and the resolution of the small scope did suffer from the noise.

 

SeaGull 2019-02-12.jpg
*click*
    

     Anyway, I start panning S now towards the Gum 8 bubble, and on the way, I come across a relatively bright patch of emission nebulosity ca. 7⁰ due S of NGC2343 in CMa OB1: Sh2-301. This nebula is at the detonation front of an ISM bubble (GS234-02) together with a string of other Sharpless nebulae in the area, such as Sh2-299, 300, (301,) 302, 305, 306, 307, 309. The bubble was blown up by sequential SN explosions 160 Myr ago at 4 kpc distance in the Perseus Arm, much like the Lindblad Ring in our Local Bubble, with its molecular clouds and OB-associations forming the Gould’s Belt:

 

Sh2-301.jpg
*click*

 

     On the way further S I dock at the small "island" of M41, which is just a beautiful view at 30x in a 3⁰ FOV of a wide field glass EP:
 

M41.jpg
*click*

 

     Thus refreshed, I finally head towards the area around Tau CMa (NGC 2362) to see if I can identify some of brightest of the emission nebulosity associated with the Gum 8 bubble (Sh2-310). The object is low at only ~8⁰ Alt, almost culminating due S, but I am able to locate the Tau CMa – UW CMa multiple star systems among the trees and aerials at the horizon. These systems are at the center of the Sh2-310 bubble, so after having spend some time on NGC 2362 (which is a beautiful tight stellar group), I now start looking for nebulosity further out in the field, --but fail to locate any...

 

Tau CMa.jpg
*click*

 

     Back inside at the desk I realize that I have to look even further out SE from Tau CMa to find the brightest Y-shaped rim of the Gum 8 bubble. I'll have to look around VY CMa, the M5 Iae red hypergiant, which is the largest known star in the universe. It is only at 8⁰ Alt when culminating, but an observation should be doable on a good night. -- We'll see grin.gif

 

     -- Allan
 


Edited by AllanDystrup, 13 February 2019 - 10:08 AM.

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#321 Vondragonnoggin

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Posted 13 February 2019 - 08:34 AM

I am thoroughly blown away by this thread. Don’t know how I missed this since Richfield observing is primarily what I do.

 

Allan this is phenomenal reading and all the other contributions from Glenn and others as well.

 

I will keep referencing this as I observe. So much material to reference already.

 

Thank you for all this! Agree there should be a collab book. I would buy instantly.

 

bow.gif


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#322 Mr. Bill

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Posted 13 February 2019 - 11:04 AM

This is a new dimension in amateur visual astronomy that I am seriously considering getting into in the future.

 

I am hoping for 60 degree afov in the near future.


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#323 Mr. Bill

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Posted 13 February 2019 - 12:16 PM

I’m hoping devices withat least 60° AFOV become more readily available. I have two that are easily 60° AFOV, but finding the gen 3 tubes for them these days is extremely rare. They are also pretty heavy compared to the current 40° AFOV devices. The tubes use a 25mm optical window instead of 18mm and are thicker than a soda can and almost as tall. The surrounding housing is very big and they weigh over 2lbs.

What is your setup and what's it going to cost to get in the game?



#324 Mr. Bill

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Posted 13 February 2019 - 02:38 PM

Thanks...cool.gif

 

Don't think Allan minds....he's inspiring others to "get in the game."

 

I'll be in line if and when he publishes his work.


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#325 AllanDystrup

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Posted 14 February 2019 - 05:21 AM

VDN, Bill -- thanks!

 

     In general I prefer to focus on observation and the nature of the observed objects here in the CN fora dedicated to Observing, while posting my experiences and opinions on telescopes, eyepieces, cameras/NVDs etc. in the appropriate Equipment fora. That said, I have occasionally also commented on my own equipment for doing DSO here in this thread, but I try to minimize this for two reasons:
 

     1: so as not to clutter up the description of the observing projects with too much peripheral information
     2: so as not to trigger recurrent and heated discussions of what is the "right" way and tools for observing the universe

 

     I realize that even including EAA and NVD observations in a CN Observing forum may be pushing the border of the comfort zone for some, but this is the way I have chosen to explore the universe with my small grab/go equipment from my suburban backyard, so if I want to share my obs. reports, this is the way I can do it.

 

     On the other hand I do understand that for many observers including extended discussions of equipment in an observing forum is crossing the line, especially if the chosen equipment for observation is based on a technology they (for whatever reason) have no interest in using, -- so I find it a reasonable compromise to post my observations and research of the astronomical objects here in the DSO forum, while relocating the discussion of observing devices to the equipment fora. I hope that makes sense...  wink.gif

__________
 

     And so, to include an observation, here's the log from my recent study of the lawn sprinkler galaxy in Leo:

 

N2903.jpg
*click*

 

     -- Allan


Edited by AllanDystrup, 14 February 2019 - 05:26 AM.

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